Cyclopentadienyl metal salts and derivatives of cyclopentadiene derived from such metal salts are important intermediates which are used in various fields such as the preparation of medicines, agrochemicals, metallocenes, etc. An effective process for the preparation of cyclopentadienyl metal salts comprises removing hydrogen atoms from cyclopentadiene with bases to synthesize corresponding metal salts, and for example, such a process using butyl lithium is known (J. Organomet. Chem., 462, 1993, 57-67).
However, the process using butyl lithium has disadvantages such that (1) used reagents are expensive, (2) it requires low-temperature facilities to perform the reaction, and (3) the reaction should be carried out at the low concentration of reagents in an industrial scale, and thus the productivity decreases, since the desired product cannot effectively be obtained if the reaction is not carried out at a low temperature, although the amount of reaction heat is large. As a matter of course, cyclopentadiene derivatives derived from cyclopentadienyl metal salts have the same problems.
Also, a process using an alkali metal hydride is known. However, this process has disadvantages such that (1) the kinds of substrates are extremely limited, (2) mineral oils, which are usually contained as a stabilizer in marketed alkali metal hydrides, should be beforehand removed, and thus the use of the alkali metal hydrides is unfavorable from the viewpoint of disaster measures, and the number of process steps in the industrial production.